[0001] The present disclosure relates to a low-chromium white iron alloy.

BACKGROUND

[0002] Low-chromium white iron alloys are generally known. However, a problem is often the rather edgy carbide crystals formed within the alloy, which may increase the brittleness of the alloy product.

SUMMARY

[0003] It is an objective of the present invention to provide an improved low- chromium white iron alloy.

[0004] According to an aspect of the present invention, there is provided a white iron alloy comprising rare-earth (RE) element. The alloy comprises RE of 0.01-0.6 wt%, Cr of 1-2 wt%, C of 2.5-4.2 wt%, Ni of 3-5 wt%, Si of 0.2-2 wt%, Mn of 0.5-1 wt%, at most 1 wt% of impurities, and a balance of Fe.

[0005] According to another aspect of the present invention, there is provided a method of preparing a white iron alloy comprising RE element. The method comprises adding an RE powder to a metal melt whereby a white iron alloy melt comprising RE is formed. The alloy melt comprises RE of 0.01-0.6 wt%, Cr of 1-2 wt%, C of 2.5-4.2 wt%, Ni of 3-5 wt%, Si of 0.2-2 wt%, Mn of 0.5-1 wt%, at most 1 wt% of impurities, and a balance of Fe.

[0006] According to another aspect of the present invention, there is provided a white iron product made from an embodiment of the alloy, or alloy melt, of the present disclosure, wherein the white iron product is or comprises any of a dispersing disc, a grinding disc, a refiner disc, an abrasion resistant plate, a mixing blade, a mixing arm or a cutting blade, preferably a refiner disc and an abrasion resistant plate.

[0007] The at most 1 wt% of impurities typically comprises a plurality of compounds other than those specified herein as part of the alloy or alloy melt, such as copper (Cu) resulting from using scrap metal as an iron source. Each of said compounds of impurity, e.g. Cu, is typically present in an amount of less than 0.5 wt%, less than 0.2 wt%, less than 0.1 wt% or less than 0.05 wt% of the alloy or alloy melt. [0008] It has now been found by the inventors that the inclusion of RE in an amount within the range of 0.01-0.6 wt% in the alloy results in finer and more rounded carbide crystal structures. The carbide crystals are more rounded and thus prevent crack formation in the alloy product. The low chromium content results mainly in M ₃ C carbide formation, where M is metal such as Fe and/or Cr to form Fe ₃ C and/or Cr ₃ C, i.e. cementite.

[0009] Different chromium carbides are formed at different chromium contents of an alloy. In steel alloys with up to about 13 wt% Cr, Cr substitutes Fe in some of the carbide phase cementite (M ₃ C, where M is metal, here Fe or Cr), forming a Cr ₃ C carbide phase which is desired for some applications.

[0010] Thus, in some embodiments of the present invention, RE is used to round off Cr ₃ C carbide crystals in a white iron alloy.

[0011] It is to be noted that any feature of any of the aspects may be applied to any other aspect, wherever appropriate. Likewise, any advantage of any of the aspects may apply to any of the other aspects. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

[0012] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein.

DETAILED DESCRIPTION

[0013] Embodiments will now be described more fully hereinafter. However, other embodiments in many different forms are possible within the scope of the present disclosure. Rather, the following embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0014] In some embodiments, the amount of RE in the alloy, product or alloy melt is within the range of 0.05-0.6 wt% or o.1-0.5 wt%, preferably within the range of o.2-0.4 wt% which maybe a preferred range in some embodiments.

[0015] In some embodiments, the amount of chromium (Cr) in the alloy, product or alloy melt is within the range of 1.6-2 wt%, which may be a preferred range in some embodiments. [0016] In some embodiments, the amount of carbon (C) in the alloy, product or alloy melt is within the range of 3.5-4 wt%, which maybe a preferred range in some embodiments.

[0017] In some embodiments, the amount of nickel (Ni) in the alloy, product or alloy melt is within the range of 3.5-4 wt%, which maybe a preferred range in some embodiments. In low-chromium alloys, a relatively high amount of nickel may be advantageous.

[0018] In some embodiments, the amount of silicon (Si) in the alloy, product or alloy melt is within the range of 0.3-1 wt%, which maybe a preferred range in some embodiments.

[0019] In some embodiments, the amount of manganese (Mn) in the alloy, product or alloy melt is within the range of 0.6-0.8 wt%, which maybe a preferred range in some embodiments.

[0020] There is typically a small amount of inevitable impurities in the alloy, product or alloy melt, e.g. if the iron (Fe) is from scrap metal. The amount of impurities is preferably at most 1 wt%. The at most 1 wt% of impurities typically comprises a plurality of compounds other than those specifically specified herein as part of the alloy or alloy melt, e.g. copper (Cu) resulting from using scrap metal as an iron source. Each of said compounds comprised in the at most 1 wt% of impurities, e.g. Cu, is typically present in an amount of less than 0.5 wt% or less than 0.2 wt%, preferably less than 0.1 wt% or less than 0.05 wt% of the alloy or alloy melt.

[0021] In some embodiments, the RE comprises or consists of cerium (Ce), lanthanum (La) and/or yttrium (Y), preferably Ce (which is easily obtainable).

[0022] The balance of the alloy, product or alloy melt is Fe. In some embodiments, the alloy, product or alloy melt comprises Fe within the range of 80-90 wt%.

[0023] RE powder is added to the metal melt to produce the alloy melt of the present disclosure. The RE powder may have a particle size distribution between 0.2 and 7 mm. The RE powder may have an RE content within the range of 25-40 wt%. The RE powder may comprise or consist of mischmetal.

[0024] The alloy melt may be used for casting a product, to obtain a white iron product. The casting is preferably by line forming, shell forming, hand forming or by 3D-printed moulds or cores. Line forming maybe preferred, but shell forming has been seen to give primary austenite formation which may be desirable in some embodiments.

[0025] In some embodiments, the white iron product is or comprises any of a dispersing disc, a grinding disc, a refiner disc, an abrasion resistant plate, a mixing blade, a mixing arm or a cutting blade, preferably a refiner disc and an abrasion resistant plate.

[0026] The present disclosure has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the present disclosure, as defined by the appended claims.